Amplifying arrangement



Dec. 17, 1935. E. 'KLmz HAL, 2,024,582

AMPLIFYINQ ARRANGEMENT Filed Oct. 10, 1932 INVENTORS ERNST KLOTZ RUDOL R NITZ E R A'Tr'oRNEY Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE ARIPLIFYING ARRANGEMENT Application October 10, 1932, Serial No. 637,050 In Germany November 26, 1931 2 Claims.

An object of our invention is to provide an improved audio frequency amplifier and one in which undesirable currents or oscillations are prevented.

A further object of the invention is to provide a novel arrangement of the input circuit of an amplifier in which a resistor is incorporated in the grid circuit at a position very close to the control grid and preferably within the socket or base of the tube.

The invention is illustrated in the accompanying drawing in which,

Fig. 1 is a schematic wiring diagram showing the circuit arrangement embodying the invention; and,

Fig. 2 is a perspective with certain portions broken away of a device embodying the invention.

We have found that in radio receivers using power amplifying tubes and also in audio'frequenoy amplifier systems that the power tubes or those in the last stage of the system are subjected to disturbing phenomena which are caused by undesirable high frequency oscillations. These disturbing phenomena may be eliminated by taking considerable precautions in the design of the apparatus and particularly by a careful arrangement of the wiring. According to our invention these disturbances are avoided, however, ln a much simpler and safer manner by arranging a resistance of the order of 1,000 ohms in the grid circuit and close to, or as near as possible to, the grid or control electrode. In order to arrange the resistor as close as possible to the grid electrode and to make the lead to the grid, not blocked by the damping resistance, as

short as possible, it has been found advisable to embody the resistor in the socket or base of the tube itself. We have also found that by incorporating the resistor in the grid itself by making the control gridof a material having a high resistance, the undesired oscillations may be prevented.

In the arrangement of Fig. 1 the audio amplifier l is connected to the last stage audio or power amplifier 2 by an iron core transformer 3 having primary 4 and secondary 5 one end of secondary 5 being connected to the cathode of tube 2 and its opposite or high potential end being connected through lead 6 and resistor 1 to the grid 8 of tube 2. The plate circuit 9 of tube 2 is shown as including a loudspeaker, diagrammatically shown at W.

We have found that when the damping resistor I which is in series in the grid circuit has a Value of the order of 1,000 ohms, undesirable high frequency or parasitic oscillations are prevented in the amplifier circuit and the tube 2 operates to 5 give faithful amplification of the received signals. We prefer to mount resistor 1 in the tube socket or base H and external to the glass envelope 2 as shown clearly in Fig. 2. One end of the resistor is connected to one of the tube 10 prongs l2 by lead l3 and its opposite end to control grid 8 by lead l4. By this construction it will be seen that the damping'resistor is mounted within the tube base and very close to the grid.

The invention has been found to be desirable 15 when used with the modern high power pentode tubes, the resistor connected in the grid circuit and preferably close to the control grid, being found to efiect proper operation of the tube as an amplifier by preventing high frequency oscil- 20 lations from interfering therewith.

What we claim as our invention is:

1. In combination, a power audio frequency amplifier tube having a plurality of electrodes including a control grid, a containing envelope for said electrodes, a base mounting for said tube, a high resistance supported in said base and external to said envelope a short lead connecting one end of said resistance and said control grid, a pin projecting from said base mounting and a short lead connecting the other end of said resistance and said pin.

2. In combination, a vacuum tube audio frequency amplifier having a plurality of electrodes including a control grid, and a containing 35 envelope therefor, a base in which said tube is mounted, an audio frequency transformer, a direct connection between the low potential end of the secondary of said transformer and the cathode of said tube, a resistor having a high 40 ERNST KLCSTZ. RUDOLF RECHNITZER. 

